Tooth inclination assessment

ABSTRACT

A tooth inclination apparatus ( 10 ) for allowing assessment of the angle of inclination of an incisor tooth or cast thereof comprises a plane element providing a flat datum surface ( 14 ) for resting against e.g. the upper molars in the maxillary plane. From the underside of the plane element projects a protractor portion ( 18 ) with a graduated angular scale ( 24 ) which measures the angular deviation of an indicator pin ( 22 ) pivoted to the plane member at ( 20 ) and moved to contact the tooth whose inclination is being measured. Other mechanical or electro-optic devices may be used to determine the inclination of the incisor relative to the datum surface.

[0001] This invention relates to the assessment of the inclination ofthe left, right, upper or lower incisors relative to a reference such asthe maxillary plane or the mandibular plane respectively, or theocclusal plane.

[0002] The evaluation of maxillary and mandibular incisor inclinationsis an important aspect of orthodontic treatment planning, assessingtreatment progress, as well as determining treatment outcome. Incisorinclination has traditionally been assessed by lateral cephalometricradiographic analysis. However, lateral cephalometric radiograph derivedaxial inclinations of incisors are prone to large digitised errors. Inaddition, radiographs may cause a small but significant mitotic risk.

[0003] It is an aim of this invention to provide a valid, reliable,simple, inexpensive and non-invasive method and apparatus for recordingincisor inclination.

[0004] According to one aspect, this invention provides a toothinclination assessment apparatus for allowing assessment of the angle ofinclination of an incisor tooth or cast thereof in or from the human oranimal body, which apparatus comprises:

[0005] a datum element defining a generally flat datum surface for beingplaced in use against two or more upper or lower molars or pre-molarsthereby to become generally aligned with the respective mandibular ormaxillary plane, and

[0006] an angular detector associated with said datum element fordetecting the angular disposition relative to said datum surface of atleast one of the upper or lower incisors respectively.

[0007] Preferably said angular detector comprises an indicator membermovably mounted with respect to said datum element and arranged in useto be moved into contact with the tooth whose angle of inclination is tobe measured, and

[0008] an angle measurer for determining the angular orientation of saidindicator member relative to said datum element.

[0009] Preferably said indicator member is pivotally mounted withrespect to said datum element.

[0010] In one embodiment said measurer comprises a graduated angularscale whereby the angle of deflection of the indicator member relativeto said datum member may be read off visually. Alternatively, saidangular detector and/or said measurer could comprise a solid statesensor which detects the angle of inclination of the respective incisoreither by detecting the angle of the indicator member if used, or bydirect detection of the angle of the incisor. The nature, constructionand operation of such electronic or electro-optic devices will be wellknown to those skilled in the art.

[0011] Preferably said indicator member extends to opposite sides ofsaid datum surface, to define a tooth contact portion to one side, and ameasuring portion to the other, to cooperate with said angle measurer.

[0012] Preferably said datum element and said angle measurer are made upfrom a folded sheet element blank e.g. of paper or card plain orlaminated, or of plastics material, suitably shaped.

[0013] Preferably said sheet element blank comprises two generallysymmetric portions which fold together to define said first element,together with a bridging tab portion which is connected to an angularscale portion.

[0014] Preferably, said indicator member includes a shaft which isrotatably located in the fold region between said two symmetricportions.

[0015] The invention also extends to a kit comprising said sheet elementblank in generally flat form together with an indicator element.

[0016] According to another aspect, this invention provides a method ofassessing the angle of inclination of an incisor tooth or a cast thereofin or from the human or animal body, which comprises applying to two ormore of the upper molar or lower molars or pre molars a flat datumsurface thereby to be generally aligned with the maxillary or mandibularplane respectively, said datum surface having associated therewith anangular detector for detecting the angular disposition of at least oneof the incisors, and thereby determining the angular orientation of saidincisor relative to said datum surface.

[0017] Preferably said angular detector comprises an indicator memberrotatable mounted with respect to said datum surface.

[0018] Whilst the invention has been described above, it extends to anyinventive combination of the features set out above or in the followingdescription.

[0019] The invention will now be described in detail by way of exampleonly, reference being made to the accompanying drawings in which:-

[0020]FIG. 1 is a side view of an embodiment of the tooth inclinationprotractor of this invention in use on a dental cast measuring theinclination of an upper incisor to the maxillary plane;

[0021]FIG. 2 is a plan view of a blank fox forming the major part of atooth inclination protractor of an embodiment of this invention;

[0022]FIG. 3 is a view of a rotatable indicator pin for use with theblank of FIG. 2; and

[0023]FIG. 4 is a side view similar to FIG. 1, but showing an embodimentof the tooth inclination protractor of this invention in use in apatient's mouth.

[0024] Referring to the Figures, the tooth inclination protractor 10comprises a blank 12 of suitable card or plastic sheet folded doubleabout fold line I to provide a flat datum surface 14. From one side ofthe blank 12 projects a tab 16 which terminates in a graduatedsemicircular protractor portion 18. Rotatably secured at the origin ofthe protractor portion 18 is the shaft 20 of an indicator pin 22. Onehalf of the pin projects below the datum surface as viewed in FIG. 1 toterminate at the scale 24 of the protractor portion 18, whilst the otherhalf of the pin projects upwardly to be pivoted into contact with thelabial surface of the incisor tooth whose surface of inclination is tobe measured.

[0025] The blank 12 may be provided with adhesive regions 26 on themeeting surfaces which define the datum surface 14, with an interruptionto receive the shaft 20 of the indicator pin. Likewise the meetingsurfaces of the datum surface and the tab 16 may carry adhesive regions.

[0026] For flat pack, the blank may be stored in a flat form withsuitable release sheets (not shown) on the adhesive regions, andinstructions on how to make up the tooth inclinator protractor bypositioning the indicator pin 22 at the correct location at the foldline I, removing the release sheets and then folding the blank aboutfold line I. Thereafter the blank is folded by 180° about fold line IIto fold the tab 16 against the blank, and then by 90° about fold lineIII to place the protractor portion 18 projecting normally from thedatum surface, and adjacent the indicator pin 22, to produce the toothinclination protractor as shown in FIG. 1.

[0027] The blank is preferably printed on one side only with thealignment markings as shown in FIG. 2. The protractor may carry lines 23on the middle of the protractor to allow overjet to be measured.

[0028] To measure the tooth inclination in say the upper (maxillary) setof teeth, the protractor is placed in the mouth so that the datumsurface 14 rests against the upper molars to define a reference surface,with the incisor whose angle is to be measured disposed adjacent theindicator pin, and the protractor portion 18 projecting downwardly. Thepin 22 is then rotated against the lateral surface of the incisor 30 atits maximum bulbosity so that the area above and below the contact isequal so that the pin 22 is then tangential to the point of contact. Theangle of inclination is then read off the protractor scale.

[0029] The measurement may be taken on a patient directly (FIG. 4) orfrom a cast taken from the patient's teeth (FIG. 1). In FIG. 4 thedevice is shown in a patient's mouth held in place by the practitioner'sthumb and index and middle fingers 32, 34, 26 respectively.

[0030] In addition, the angle of inclination of the tooth may bedetected by means other than mechanical, e.g. electronically or by laseror an optical device, such as a solid state sensor which detects theangular disposition of the incisor or the indicator pin.

1. A tooth inclination assessment apparatus for allowing assessment ofthe angle of inclination of an incisor tooth or cast thereof in or fromthe human or animal body, which apparatus comprises: a datum elementdefining a generally flat datum surface (14) for being placed in useagainst two or more upper or lower molars or pre-molars thereby tobecome generally aligned with the respective mandibular or maxillaryplane, and an angular detector (18-24) associated with said datumelement for detecting the angular disposition relative to said datumsurface (14) of at least one of the upper or lower incisorsrespectively, characterised in that said angular detector (18-24)comprises an indicator member (22) pivotally mounted with respect tosaid datum surface (14) and extending to opposite sides of said datumsurface, to define a tooth contact portion to one side, and a measuringportion to the other, and an angle measurement device (18) associatedwith said datum surface (14) to allow the angle of deflection of theindicator member (22) relative to the datum surface (14) to bedetermined,
 2. A tooth inclination assessment apparatus according toclaim 1, wherein said angle measurement device (18) comprises agraduated angular scale (24) whereby the angle of deflection of theindicator member (22) relative to said datum surface (14) may be readoff visually.
 3. A tooth inclination assessment apparatus according toany of the preceding claims, wherein said datum element and said anglemeasurement device (18) are made up from a folded sheet element blank(12).
 4. A tooth inclination assessment apparatus according to claim 3,wherein. the blank (12) is made of paper or card.
 5. A tooth inclinationassessment apparatus according to claim 6, wherein the paper or card islaminated or coated with a waterproof or water resistant coating.
 6. Atooth inclination assessment apparatus according to claim 5, wherein theblank (12) is made of plastics material.
 7. A tooth inclinationassessment apparatus according to any of claims 3 to 6, wherein saidsheet element blank (12) comprises two generally symmetric portions.which fold together to define said datum element, together with abridging tab portion (16) which is connected to an angular scale portiondefining said angle measurement device.
 8. A tooth inclinationassessment apparatus according to claim 9, wherein said indicator memberincludes a shaft (20) which is rotatably located in the fold regionbetween said two symmetric portions.
 9. A kit for making a toothinclination assessment apparatus according to any of claims 3 to 8,comprising said sheet element blank in generally flat form together withan indicator member (22).
 10. A tooth inclination assessmentapparatus-according to claim 1 or claim 2, wherein said datum elementand said angle measurement device (18) are integrally formed of mouldedplastics material.
 11. A method of assessing the angle of inclination ofan incisor tooth or a cast thereof in or from the human or animal body,which comprises applying to two or more of the upper molar or lowermolars, or pre-molars, a flat datum surface (14) thereby to be generallyaligned with the maxillary or mandibular plane respectively, said datumsurface (14) having associated therewith an angular detector (18-24) fordetecting the angular disposition of at least one of the incisors, andthereby determining the angular orientation of said incisor relative tosaid datum surface 14, wherein said angular detector (18-24) comprisesan indicator member (22) pivotally mounted with respect to said datumsurface (14) and extending to opposite sides of said datum surface, todefine a tooth contact portion to one side, and a measuring portion tothe other, and an angle measurement device (18) associated with saiddatum surface (14) to allow the angle of deflection of the indicatormember (22) relative to the datum surface (14) to be determined.